OBJECTIVES: Cancer patients are at high risk of venous thromboembolism (VTE), provoked by the cancer, chemotherapies or co-morbidities. The CATCH trial investigated the benefits of extended treatment with tinzaparin (LMWH) versus warfarin for the prevention of recurrent VTE events in cancer patients experiencing a VTE.  We aim to describe the baseline patient-reported health-related quality-of-life (HRQL) and the impact of having experienced a VTE within this very large data set in cancer-associated thrombosis. METHODS: The CATCH trial randomised 900 patients with active cancer from 32 countries. EQ-5D-3L data were collected at baseline and every month for seven months. We chose to apply the UK preference weight set and explored the baseline data which captured the acute phase of VTE.  Exploratory univariate analyses tested the effects of covariates including age, gender, metastatic status, primary site of cancer, ECOG status, and history of VTE.  RESULTS: At baseline, in the acute phase of VTE, patients reported quite poor HRQL (mean EQ-5D score: 0.52) with no difference between the treatment arms.  Women reported significantly worse HRQL than men (0.49 and 0.56), whereas there was no significant difference across age groups. Patients who had both symptomatic DVT and symptomatic PE reported the worst mean score (0.46).  Patients with higher ECOG score had lower HRQL, whereas similar mean scores were seen for metastatic status and varying scores across different cancers (brain, breast, lung, hepatobiliary, upper GI, lower GI, genitourinary, prostate, gynaecologic, haematological). Latin American and Asian patients reported lower scores of HRQL than patients in other regions. CONCLUSIONS: Compared to EQ-5D estimates reported in the literature for cancer patients, data from this large trial of cancer associated thrombosis shows that experiencing VTE has a significant additional impact on HRQL.  Women quality of life seems to be affected the most.